ppmBatch is described as 'allows you to analyze and normalize your audio files according to various broadcasting loudness standards. It batch processes files in multiple real time and provides intuitive user feedback about each file's compliance status and processing progress' and is an app in the Audio & Music category. There are four alternatives to ppmBatch for Mac, Windows and Linux. The best alternative is MP3Gain, which is both free and Open Source. Other great apps like ppmBatch are QMP3Gain (Free, Open Source), MP3 Normalizer (Paid) and Sound Normalizer (Paid).
A free automatic mp3 volume normalizer. MP3Gain analyzes and adjusts mp3 files so that they have the same volume. There is no quality lost in the change because the program adjusts the mp3 file directly, without decoding and re-encoding
Graphical user interface front end supporting MP3Gain engine which analyzes and losslessly adjusts mp3 files to a specified target volume. A complete re-creation (made in QT4) of the original MP3Gain GUI, however it can be run on more platforms.
MP3 Normalizer improves the quality of MP3 files. It amplifies too quiet audio or decreases the volume of too loud files or their parts automatically. It also smoothes sound peaks and clicks in MP3 tracks.